Part 2: Background

Inquiry into procurement of work by Westland District Council at Franz Josef.

Our inquiry was into a decision made by the Council to carry out work to protect the Franz Josef wastewater plant from flooding by the Waiho River.

The wastewater plant was built in the late 1970s, and is owned and operated by the Council. The wastewater plant consists of two oxidation ponds situated west of Franz Josef and next to the Waiho River. An infiltration gallery discharges treated wastewater into the river.

There is a history of problems associated with the wastewater plant, including ongoing non-compliance with the terms of its discharge consent and concerns about flood risk.

Because of Franz Josef's flood-prone and earthquake-prone location, the Council and the Franz Josef community as a whole are also facing difficult decisions about the long-term future of the town.

In this Part, we describe these and other challenges the Council was facing when it decided to carry out the work.

The flood-prone Waiho River

The Regional Council has described the Waiho River as "among the most difficult New Zealand rivers to manage". The riverbed is building up with gravel and sediment at a rapid rate. This process, referred to as "aggradation", reduces the capacity of the river's channels when flooded and makes the river very hard to predict and control. The river can switch course rapidly under flood conditions and quickly threaten neighbouring properties and land.

Many studies have tried to understand the dynamic nature of the flood hazards posed by the Waiho River. In 2014, the Council commissioned a report that focused specifically on the risks to the wastewater plant. The report found that:

  • the location of the wastewater plant made it extremely vulnerable to damage by large floods;
  • there was a very high chance that by 2019 the Waiho River would break its banks and inundate the wastewater plant, and a reasonable chance that this would happen before 2016; and
  • ongoing aggradation could eventually lead to the river carving a permanent channel through the site of the wastewater plant.

Wastewater treatment plant flooded in March 2016

The wastewater plant was protected from the Waiho River by a raised access road that followed the natural curve of the land and riverbed. Because it was raised, the access road provided some river protection, but it was not a stopbank.

In March 2016, the flood risk became a reality. The Waiho River flooded and burst its banks near the wastewater plant. The river swept through the wastewater ponds and nearby properties, and 186 people had to be evacuated. Sewage flowed into the river. The ponds were severely affected by the flood. Council staff estimated "near 80% damage to the earthworks and the treatment process".

Immediately after the flood, NZTA rebuilt the breached section of the raised access road.

Environment Court orders a replacement plant in November 2016

For several years, the wastewater plant had been periodically discharging non-compliant effluent into the Waiho River. The wastewater plant was often overloaded due to increased tourism to Franz Josef. There were also ongoing problems with the infiltration gallery.

The Regional Council had issued several abatement notices and, in 2015, took enforcement action against the Council for continued non-compliance. The enforcement action resulted in an Environment Court order in November 2016 that required the Council to, among other things, have a fully operational replacement plant by 30 April 2018.

Options for a new wastewater treatment plant

By the time the Environment Court order was made, the Council had already received a detailed report from Opus International Consultants Limited (Opus) on options for a new wastewater plant.

The report compared several options based on either oxidation ponds or a compact "high rate wastewater treatment plant" at different locations. The report recommended a mechanical plant located out of the flood hazard zone and very close to the residential/commercial-zoned area of the town.

The Council received the Opus report not long before the October 2016 local government elections. Public interest in what needed to be done about upgrading the wastewater plant was high. The Council decided to wait until after the local government elections before deciding how to respond to the report.

The long-term future of Franz Josef – the Tonkin + Taylor report

At the same time as the Council was considering what to do about its wastewater plant, broader discussions were also taking place in the community about how to respond to the significant flood and earthquake risks faced by Franz Josef.

In March 2017, the Regional Council, with funding from central government, had engaged Tonkin + Taylor Limited and Ernst & Young to identify and assess options for managing the flood and earthquake risks (the Tonkin + Taylor report). A wide range of options were explored, including moving the town to Lake Mapourika. These broader discussions complicated the decisions that needed to be made on how to fix the town's immediate wastewater problems.

The Council received a confidential draft of the Tonkin + Taylor report in June 2017 just before it made the decision we are inquiring into. The report was made public in October 2017. The published report presented three packages of options. All options involved relocating the wastewater plant.


In summary:

  • The Waiho River is notoriously flood-prone and difficult to manage.
  • Because the wastewater plant is located next to the river, it was at permanent risk of flooding.
  • The wastewater plant was flooded in March 2016, causing significant damage to the plant and expense and disruption to the community.
  • As a result of ongoing non-compliance issues, the Environment Court ordered the Council to decide on a replacement for the wastewater plant by the end of 2016, and to have a fully operational replacement wastewater plant by 30 April 2018.
  • Because of the flood risk, the Council's consultant engineers had advised that the wastewater plant had to be replaced by a plant outside of the flood hazard zone.
  • The Tonkin + Taylor report into managing the natural hazard risks faced by Franz Josef had also recommended relocating the wastewater plant.
  • The Council had decided to postpone making a decision about the wastewater plant pending the outcome of the local government elections in October 2016.